Outcomes of intraoperative radiation therapy in the treatment of advanced head and neck cancer

Objectives: A retrospective match-paired analysis of the outcomes of salvage surgery with intraoperative radiation therapy in comparison to salvage surgery alone in the treatment of advanced stage recurrent head and neck cancers at the University of Louisville Hospital. Materials and Methods: Patients with at least 2 years of follow up from the date of treatment (30) were reviewed for efficacy of therapy and overall outcome in comparison with match-paired control patients treated with salvage surgery alone. Patients were divided into 3 groups based upon the final surgical resection margins at the time of IORT delivery and/or surgical salvage: negative margins, microscopic residual disease, and gross residual disease. The disease free and overall survival were followed and compared across groups and pathologic resection outcomes through Kaplan Meier survival curves and Cox regression analysis. Results: A total of 60 patients met the inclusion criteria for this chart review, 30 patients having been treated with IORT and 30 match paired control patients treated with salvage surgery alone. The population predominantly included patients with a diagnosis of stage 3 and stage 4 squamous cell carcinoma of the upper aerodigestive tract. Patients in the IORT treatment group received on average 1500cGy at 9mEv. Pathologic review found that patients in the control group were more likely to obtain a negative surgical margin at the time of salvage resection than those patients in the IORT group. No statistical differences were identified between groups for disease free and overall survival. Hazard ratio analysis identified gross positive margins as the only statistically significant risk factor for decreased overall and disease free survival among all patients. Conclusions: Intraoperative radiation therapy has become a growing treatment modality in patients with head and neck cancer. Despite attempts at an accurate match-paired analysis, patients within the IORT group were chosen to receive this therapy due in part to the aggressive nature and/or location of their tumors. This subtle selection bias amongst patients with recurrent stage 3 and stage 4 carcinomas of the head and neck likely contributes to an altered perception of the efficacy of IORT. As would be expected, the significance of obtaining negative surgical margins is demonstrated through the increased time to recurrence of disease and overall survival in this patient population was demonstrated in this study.